The field of art to which this invention is directed is polysaccharide derivatives.
Polygalactomannans, particularly the naturally occurring guar gum and locust bean gum, have been known for some time and have found many industrial uses. To improve the performance of these gums and to widen their fields of use, polygalactomannans have been modified by reaction with various reagents to form derivatives of the gums. Examples of such derivatives are hydroxyalkyl ethers of polygalactomannans, aminoalkyl ethers of polygalactomannans, long chain alkyl ethers-hydroxyalkyl ethers of polygalactomannans, and aminoalkylether-hydroxyalkyl ethers of polygalactomannans.
Hydroxyalkyl ethers of polygalactomannans are described in U.S. Pat. No. 3,326,890. Aminoalkyl ethers of the gums are disclosed in U.S. Pat. No. 3,498,412. Mixed derivatives containing long chain alkyl ether groups and hydroxyalkyl ether groups are described in U.S. Pat. No. 4,870,167. Mixed derivatives containing tertiary aminoalkyl ether groups and hydroxyalkyl ether groups are disclosed in U.S. Pat. No. 4,918,181.
Hydrophobically-hydrophilically modified polygalactomannans are disclosed in U.S. Pat. No. 4,960,876.
Hydrophobe substituted water-soluble polysaccharides which contain quaternary ammonium substituents are described in U.S. Pat. No. 4,663,159.
Polygalactomannans and their derivatives find extensive use as thickeners for aqueous systems in many industrial applications. As disclosed in U.S. Pat. No. 4,870,167, hydrophobically modified non-ionic polygalactomannans are efficient thickeners for aqueous fluids, either alone or combined with surfactants.
After the purpose for using the thickened aqueous fluid has been served, it is often desirable to lower the viscosity of the fluid. This lowering of viscosity is accomplished by using a "breaker" which acts on the water-soluble polymer to reduce its molecular weigh and to thin the fluid in which it is dissolved.
In commonly assigned U.S. Pat. No. 4,647,385, the viscosity of aqueous solutions of water-soluble polymers is reduced by the addition of alkali metal or alkaline earth metal salts of hypochlorous acid plus tertiary amines.
When tertiary amino polygalactomannans or the double derivative, i.e., dialkylaminoalkyl-hydroxyalkyl ethers of polygalactomannans, are used, as thickeners for aqueous fluids, the viscosity of the fluids can be reduced by the addition of an alkali metal or alkaline earth metal salt of hypochlorous acid, or a chlorinated isocyanurate. These reactions are disclosed in commonly assigned U.S. Pat. No. 4,941,537 and U.S. Pat. No. 4,918,181.